1. Field of the Invention
This invention relates to a process for preparing polyolefins by use of a novel polymerization catalyst. More particularly, it is concerned with a process for preparing polyolefins by polymerizing or copolymerizing olefins in the presence of a catalyst, said catalyst comprising a combination of solid component which is obtained by copulverizing (1) a magnesium halide and/or a manganese halide, (2) an aromatic hydrocarbon, (3) a tetravalent titanium compound and (4) a trivalent titanium compound, and a mixture which consists of (5) a trialkylaluminum and (6) an organoaluminum compound of the general formula AlR.sub. n X.sub.3-n wherein R is alkyl having 1 to 10 carbon atoms and may be the same or different, X is halogen and 0&lt; &lt; 3, whereby the yield of polymer per solid and that per transition metal are remarkably increased resulting in the process dispensing with the step of removing residual catalyst in the polymer and at the same time the bulk density of the resulting polymer is hightened, the molecular weight distribution thereof is widened and consequently the fluidity of the polymer in a molten state is improved.
2. Description of the Prior Art
Heretofore, in the technical field of this sort, applicant of the present invention has filed a patent application (Japanese Patent Application No. 5014/75) on his finding that if olefin polymerization is made by use of a catalyst which comprises a combination of a solid component obtained by copulverizing a magnesium halide and/or a manganese halide, an aromatic hydrocarbon and a titanium compound, and an organoaluminum compound and/or an organozinc compound, the catalyst activity is remarkably increased and also the bulk density of the resulting polymer is remarkably improved.
On the other hand, to the manufacturers of polyolefin it has been a matter of great concern to develop a catalyst whose activity is high enough to dispense with the step of removing residual catalyst and which affords a polyolefin having a sufficiently high bulk density and a good melt fluidity.